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Shallow Waters

Sunday, August 24, 2014

A well-camouflaged octopus encountered during a survey at the Endurance Oregon Shelf site (80 meters water depth).

Photo Credit: NSF-OOI/UW/CSSF, Dive R1756, V14

Exposed gas hydrate (a clathrate of water ice that forms around methane) observed in Einstein's Grotto at the Southern Hydrate Ridge summit. Large bubbles were seen escaping intermittently from the crevice, indicating an active methane seep. A rockfish is sheltering within the grotto as well.

Photo Credit: NSF-OOI/UW/CSSF, Dive R1754, VISIONS14

The end of Leg 3 is approaching rapidly, and we have successfully met every goal for this leg of the VISIONS '14 expedition, including some that were not able to be completed during Leg 2. The final Leg 3 objectives were to deploy and connect the Slope Base deep profiler mooring, which was completed on August 23rd. This was a challenging deck operation, due to the depth of the site (2900 meters) and the weight of the mooring line and anchor required to deploy at that depth. However, the engineering team worked day and night, through some adverse conditions, to complete the mooring deployment. That was followed by a ROPOS dive which plugged the mooring into the seafloor network and tested the profiler functionality. It was found to be working perfectly, and so we moved on to accomplishing some additional tasks from later legs of the cruise, in an attempt to save time and money in the event that the weather or some technical issue cut into the available cruise days later in the summer.

We dove on Hydrate Ridge to identify deployment sites for Leg 4, and to look for active methane bubble plumes. We found some exposed gas hydrate (a clathrate, or a form of water ice that forms under high pressure, low temperature, methane-saturated conditions, with a methane molecule trapped within the crystal lattice) and active seeping of methane bubbles in and around Einstein's Grotto. This was important because the grotto is a major instrument deployment site that is within cable range of the low-voltage node at the Southern Hydrate Ridge OOI site.

We also were able to move into even shallower water (specifically 80 meters, or about 260 feet) and survey the Endurance Oregon Shelf site to make sure that it a) was a suitable deployment site for the medium-powered junction box and science sensors, and b) that there were no hazards to the cable or obstructions that might require removal or a rerouting of infrastructure. The survey found no hazards, and we observed a completely different type of seafloor ecosystem: a sandy bottom, highly productive coastal environment, with many small flatfish and euphausiids (a group that includes krill, small shrimp-like crustaceans), large Metridium anemones, and giant starfish (Pycnopodia, or sunflower sea stars).

We have now completed all cruise activities, as a second dive in this area was precluded by weather (the wind is up above 20 knots and the waves are rising). We'll be back in Newport by morning, with a complete success under our belts. On to Leg 4!